Microwaves with turning knobs (example [0], maybe not the best, but you'll get the point) can have arbitrary power setting. My personal, electronic microwave,

Microwaves with turning knobs (example [0], maybe not the best, but you'll get the point) can have arbitrary power setting. My personal, electronic microwave, has values 125/250/500/750W so not completely exponential (I guess, that's what you meant?). One thing is, you can always (?) set arbitrary time, so you can compensate to gaps in power settings. Other thing, maybe electronics are more simple with power settings like these? When I see exponential settings I would always think of analogy to photography and 'f-stops' [1]. Some devices have exponential settings due to the physical nature of something, but is it the case with microwaves, I don't know. [0] http://www.firstiraq.com/sites/default/files/products/5002-1_neu.jpg http://www.firstiraq.com/sites/default/files/products/5002-1... [1] https://en.wikipedia.org/wiki/F-number https://en.wikipedia.org/wiki/F-number